The present invention relates to a method of increasing productivity and recovery of wells in oil and gas fields.
Method of the above-mentioned general type are known. A method of hydraulic fracture of underground layers for formation of horizontal slots is known, as disclosed for example in U.S. Pat. No. 3,965,982. In this method upper and lower packers are installed in a well opposite to the layer in contact with a surface of the layer.
Another method for increasing permeability of productive layers is based on introduction of clay wedging agent into a fluid, as disclosed in U.S. Pat. No. 3,976,138.
A further method is used for producing hydraulic fracture in productive layers with the use of viscous solutions of surface-active substances, as disclosed for example in U.S. Pat. No. 4,007,792. With this method a pressure in the well is increased to a value causing formation of cracks in the rock, and the pressure is maintained between 0.5 and 6 hours. The pressure is then reduced, and the material is removed from the well.
Also, a method of multiple fracturing of underground layers is known, in which in order to fracture the layer which is opened by a well, a working fluid is pumped through the well into the layer, and a particulate wedging material is introduced into the cracks. Then a working fluid is pumped through the well into the layer until the layer is fractured, and the particulate wedging material is introduced into the newly formed crack. This method is disclosed in U.S. Pat. No. 3,998,271.
A further method of “wedging” of cracks in productive layers includes introduction of a viscous fluid, so that the hardenable fluid penetrates into the cracks and is retained in them. Then the introduction of the viscous fluid is stopped so that the crack remains open until the hardenable fluid hardens and spreads the crack. This method is disclosed in U.S. Pat. No. 4,029,149.
Finally, a method for fracturing of productive layers by means of an acid foam is known as well. In accordance with this method a gel-like solution having a certain pressure and containing a surface active substance and an inert gas is introduced for forming slots in the layer. This method is disclosed in U.S. Pat. No. 4,044,833. Other methods are known as well.
The known methods are based on the concept of creating a hydraulic connection between a productive layer and a group of layers in a well through a low-permeable or practically impermeable near-well zone which is characterized by increased concentrations of stresses. Even if the near-well zone in the area of a productive layer does not have a poor permeability, the use of hydrofracturing not always leads to positive results. As a rule, the direction of the hydrofracturing changes along the layer, which leads to connection of the layer with water-carrying horizons and stops an industrial flow of oil/gas. In this case it is also not possible to connect simultaneously several wells for performing corresponding works.